>>11309400Bachmann do some decent N gauge set and LGB does some nice sets in G. For Brits, Hornby and Bachmann for OO, Hornby for TT and Graham Farrish in N. I forget whether Dapol make sets or not.
If buying used sets and locomotives, Fleischmann is the best for HO and I would say Aurora Postage Stamp is decent for N, but always do your homework. Tyco and Life-Like are the cheapest usually and are just fine for beginners, especially at their price point.
If the gauge is not S, Gauge 1 or any of the above, buying used is generally not feasible. I would say this especially good for Z as the MTL models have a number of issues and were more created as a novelty. That dude not mean that they cannot be good runners, but they are not beginner friendly just because of how often they need to be serviced.